Wireless network drops when copying large files

I have a dlink WUA-1340 on a HP Pavilion Windows Media Ctr 2005 box where, I have connectivity until I try to copy a file to/from the box at which time i can no longer ping the default gateway though, it does show connected.

The dlink connection utility shows 70% signal at 54mbs and, I have moved the antenna around. In addition, other machines do not have any issue w/the link or noise.

I've tried (to no avail):
- disable windows wireless zero config and use the dlink utility.
- change the frequency/channel
- change the fragmentation & rts threshold
- looking for a new driver (none available) or a KB article at MS.

Any ideas appreciated.

Are you saying the problem happens immediately when you try to copy a large file, or after it has been copying a while with no other activity? And does this happen no matter what machine is copying to/from the media center?

Is there any way to set the WUA-1340 to wireless B? Not that it would be a great solution, but it would be a way to test its compatibility with the wifi access point.

Another experiment might be to give the media ctr a static IP. Sometimes this stabilizes a dropping connection.